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18 Posts
Discussion Starter · #1 ·
First of all ,as a mechanic had suggested ,I parked my '76 280-Z in my drive-
way cold and started it up and ran the tac up to2500 RPM .My fuel pressure
gauge read about 30 PSI and my manifold vacuum was about 18 PSI , and the
temp. gauge was at the half way mark .
It ran for an hour and then it started to misfire .The RPM dropped to 1500,
the manifold vacuum dropped to 14 psi and the fuel gauge was showing "0".
It ran for another 3 to 4 min.
getting progressively worse and the gauges getting lower & lower ,until
it stalled all together.I think that the tac followed the engine slowly to a
stop .The next day I started it up again [she started right up ] and ran her up to
2500 RPM . Well after running her for two hours with no problem my gas
gauge was getting to empty ,so I turned her off for the day.
Hello again ,well I started my car again this afternoon ,the first time I've
tried since I turned it off yesterday and it started right up .I ran it @ 2500
RPMs as a mechanic has suggested to me . I ran her
for an hour and a half with out any problems so I turned it off .Then
I remembered that in the past while driving around town that sometimes after
driving to the store ,when I come back out and try to start it up it won't
start or I may drive a few miles it will stall .So after it had been off for no
more than a half hour I went back out to see if it would start again and it
did ,but after no more then 10 minutes @ 2500 RPM it started missing and
smoking .
As the engine sputtered and stalled the tac followed the motors up and down fluctuations
until it finally stalled completely after trying to run for a minute or two. The fuel gauge
read about 30 PSI during this time .After an other half an hour I thought that I'd try to
start it up again and it started right up again .
So right now as I'm writing this E-mail the car is out there running @ 2500 RPM and has
been for a half an hour now .Do you still think it the ignition mogul ???
HOLD ON I was wrong as I was finishing up on this e-mail I heard the car out in the
driveway RPMs drop .So I went out and sat in it for 20 some odd minutes .
The fuel gauge is showing 0 [ car is still out there running ] and the tac is slowly
fluctuating between 2000 &2400 Rpm ,the vacuum is between 18 & 16 PSI ,the
temp gauge is well below the half way mark .It's running a little ruff but not
bad ,no smoke or anything .I could hardly breath out there earlier when it
stalled out .Well I guess it not going to die by it self and the gas gauge is getting
down to empty again , I put five gallons in it from a gas can earlier .It's been about
40 minutes now and she's still running with 0 fuel pressure.I turned the car off
and opened the gas valve I have put in the gas line a long time ago so as to
regulate the fuel [Sometimes it won't run unless I squeezes of the gas ,it's like it
get to much gas at times and won't run until I turn it down to a slow stream ]
I tried to restart it again right away and it wouldn't start ,the fuel pressure was
at 40 PSI .
I have a new gas pressure regulater and fuel filter ,I have put a valve in my gas
line which I can turn down if she won't start at times and if I restrict the gas flow
she usually will start right up and I can drive on .Usually if she stalls on the
road the fuel gauge will show 40 PSI .If I turn the gas valve down and pull the
fuel line off and relieve the pressure she will start again .It's like it's getting to
much gas ,but the fuel pressure is only 32 to 42 psi .

· Registered
3,319 Posts
How strange! It could be that your 'hand regulator' is compensating for an overly rich condition. I would start by checking the coolant temp sensor and related connectors in the harness back up the line, since it does have a temp related condition (when you shut it off then restarted a short time later). Check the return line for clogging also. Try something else too- open up the gas cap when it starts running badly and see if the tank is building up pressure, or vacuum. You could be pressurizing the tank and allowing it to run with '0' pressure (that is REAL weird!). Pressure at the fuel filter (that is where the gage is at right?) should be about 36 psi at idle and up to maybe 40 psi under acceleration (lower manifold vac). This should be a consistant reading (minor variations are ok). I would want to remove the valve and find out what it is doing under 'factory spec' setup conditions. Somehow your valve is compensating for some other condition. Obviously the problem is going to be in finding it! A clogged return line can cause an overly rich condition.

· Registered
18 Posts
Discussion Starter · #3 ·
Me again ,thanks for your responds ,I forgot to mention that I have no pressure in my gas tank because
I have a hole in the top that I can't see ,but leaks if I fill it all the way up .Could this be the
problum,John .
PS: I just went out and she started right up and is now out there running @ 2500 rpm , and with 32
psi fuel pressure ,18 lbs vacuum and temp at about the half way point .My gas valve is opened all the
way up also ! If she doesn't stall in a half hour or so, I'll turn her off and see if she starts and runs
for a while again .

· Registered
18 Posts
Discussion Starter · #4 ·
Well I ran her for about a half an hour and no stall ,so I turned her off . Then I noteiced that as I sat
there looking at the fuel gage it was very slowly going up and after a minute or two it had reson
from 32 up to 40 psi .This was done with the engine off and the fuel pump not running ???
So I restarted her and she only ran for 10 to 15 seconds and stalled ,I tried to restart with out
sucsesss . I then pulled off the fuel line at the engine steal tub and the gas flowed back at me from
the engine side not the gas tank side .I then put the fuel line back on and went and started her right
up .She's now been out there running fine for the last half an hour .
Well she just stalled again ,so I pulled off the fuel line from the engine agian to releave the pressure
and tried to restart .It only turned over and over ,no starty ! The fuel gage is showing 40 psi and the
engine temp. is at the half way point .????

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15 Posts
If you hadn't said you replaced the fuel pressure regulator, I would have bet that was your problem especially if you pull the dipstick and smell gas in the oil. A leaky injector maybe?

· Registered
18 Posts
Discussion Starter · #6 ·
7pm : just got home and as I supspected the car started right up ,it always dose if you wait long
enougth .I'll try playing with it again tomarrrow ! Over & out ,John

· Registered
3,319 Posts
It is possible that just from engine heat that the pressure could rise some while sitting. I think I would blow out all the lines especially back to the tank both supply and return (need to blow out the supply with the fuel pump disconnected) make sure the filter is clean, and also check that the vacuum line for the fpr is not cracked. Don't think a hole in the tank would cause the problem, but a clogged pickup or line might give you some very strange readings and intermittant problems.
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